Re: Database design, Keys and some other things

From: David Cressey <david.cressey_at_earthlink.net>
Date: Wed, 28 Sep 2005 13:13:53 GMT
Message-ID: <lGw_e.4989$vw6.1351@newsread1.news.atl.earthlink.net>

"x" <x_at_not-exists.org> wrote in message
news:dhbjde$tru$1_at_domitilla.aioe.org...
> Then, after the translation of this model to the relational model, the
date
> become the attribute of some relation (not of some entity) and the problem
> "which is the entity of this attribute ?" is solved.

The problem is not so much solved as obviated. It's not quite the same thing.

We can carry out a whole class of relational transformations on the data that give the same result, and have the same validity, regardless of the ultimate semantics of the data.

However if, at some future time, we get deeply involved in the meaning of the data, sooner or later the question that's obviated by the relational model will re-emerge. That's not to say that the RM doesn't achieve something of value by abstracting this question out of the logical model. It does.

Much of mathematics is about using the power of abstraction to good advantage. Received on Wed Sep 28 2005 - 08:13:53 CDT